DT 65 dies when engaging throttle

[Coosa]

I have a 1988 dt65. I recently rebuilt carbs for the 3rd. time. I am positive that they are surgically clean. The fuel pump has been rebuilt, and new fuel lines,tank, primer bulb and in-line fuel filter was installed.I also made sure the fuel filter on the motor was clean;however, when the motor is trimmed down and the throttle is engaged the motor dies.If I trim the motor up, almost out of the water, and then engage throttle I have no problem. Why is the back pressure giving me trouble? I have set the idle air screws to factory specs.It still seems to be running lean at low RPM's.

 

[bossee]

Re: DT 65 dies when engaging throttle

Hi,<br /><br />1. Did You use 3 Suzuki carburator kits when You rebuilt the carbs or did You just clean them?<br />Like this:<br /><br /> Link <br />Notice the repair kit include new needle valve.<br /><br />2. Same with fuel pump, did You replace the rubber diaphragm set or did You just clean the fuel pump?<br />Was the reed valve OK?<br /><br />3. Did You set float in carburator to specified height? Have the floats been replaced?<br />Was the needle valve and seat in carburator OK<br />(not worn)?<br /><br />4. Have You set idle RPM to about 700 while in gear after warm up?<br /><br />5. Do You use NGK B8HS-10 spark plug with gap 0,8-0,9 mm / 0,31-0,35 inch?<br /><br />6. How do the spark plugs look like if You remove them?<br /> Link

 

[Coosa]

Re: DT 65 dies when engaging throttle

thanks Bo, <br />you have helped me tremendously once before! I did use new kits on the carbs. I set the floats to be parallel with the carb body while turned upside down.needle valves move freely.I don't have a tach, so I am guessing on RPM range; however, I never set idle while underway.the oil enjection recently quit pumping to cylinder #1 and #2. I am looking at plugs now, and they appeared to have carbon build up.Could a float be sticking even though I have replaced needle valve and seat? They are the original floats.

 

[Coosa]

Re: DT 65 dies when engaging throttle

Forgot to add that the oil enjection has been repaired.

 

[bossee]

Re: DT 65 dies when engaging throttle

OK, lets see:<br /><br />1. Carburator kit installed with new needle valve+seat. Good.<br /><br />2. Did You install a new rubber diaphragm set in fuel pump?<br /><br />3. OK, orginal float in use.<br />You must adjust the float height also:<br /><br />0.39-0.47 inch (for a DT65 1988)<br /><br />If not within specification adjust the height by bending the adjustment tab.<br /><br />

<br /><br />4. Idle RPM set to 700 in gear - You have not done that but impossible since You have no tachometer. You really need a tachometer, not for this but so You know it will rev about 5500 at WOT.<br />Maybe a Tiny Tach?<br /><br /> Link <br /><br />5. I assume You use correct spark plugs and gap.<br /><br />6. Some carbon on spark plugs.<br />Check again in the Link I gave in no 6 above.<br />There are some examples what can cause carbon built up on spark plugs. One they mention is out of adjustment float height. Another low cyl compression (see below).<br /><br /><br />Also You say no 1 and 2 cyl had an oil injection problem. That could be a real problem - make a compression test on all cylinders and compare results. If a cyl has 15 psi (103 kPa) or more difference compared to other cylinders it indicate a problem on that cyl.<br />Rule of thumb - a 25% lower compression on a cyl compared to highest value you get on a cyl in a test indicate a problem.<br />If the no 1 and 2 cyl got no lubrication because the oil injection failed while running the outboard it could have damaged the cyl, piston, rings, bearings.

 

[Coosa]

Re: DT 65 dies when engaging throttle

Bo, <br /><br />I have installed a new fuel pump diaphragm set.I broke down carbs and checked the float distance as you suggested. The middle carb float was a little off mark, so I corrected.I also checked the spark plug gaps and found they were not even close to 0.8-0.9, more like 0.12. I corrected that problem as well.Compression in all 3 cylinders checked out(thankfully).I appreciate the link to "tiny-tach" and the fancy exhibits.I will look into purchasing a tach.you are very helpful.Thanks for your time.I will keep you posted on the results.

 

[Coosa]

Re: DT 65 dies when engaging throttle

Bo, <br /><br />I took her to the river today and she ran better than ever! I believe the gap adjustments on the sparks plugs were the remedy.Thanks again for your help.

 

[bossee]

Re: DT 65 dies when engaging throttle

Coosa,<br />Glad I could help a little.<br />But You did the all work, and correct.<br />Happy boating!<br />/Bo

 

[Stuber59]

Re: DT 65 dies when engaging throttle

OK, lets see:<br /><br />1. Carburator kit installed with new needle valve+seat. Good.<br /><br />2. Did You install a new rubber diaphragm set in fuel pump?<br /><br />3. OK, orginal float in use.<br />You must adjust the float height also:<br /><br />0.39-0.47 inch (for a DT65 1988)<br /><br />If not within specification adjust the height by bending the adjustment tab.<br /><br />

<br /><br />4. Idle RPM set to 700 in gear - You have not done that but impossible since You have no tachometer. You really need a tachometer, not for this but so You know it will rev about 5500 at WOT.<br />Maybe a Tiny Tach?<br /><br /> Link <br /><br />5. I assume You use correct spark plugs and gap.<br /><br />6. Some carbon on spark plugs.<br />Check again in the Link I gave in no 6 above.<br />There are some examples what can cause carbon built up on spark plugs. One they mention is out of adjustment float height. Another low cyl compression (see below).<br /><br /><br />Also You say no 1 and 2 cyl had an oil injection problem. That could be a real problem - make a compression test on all cylinders and compare results. If a cyl has 15 psi (103 kPa) or more difference compared to other cylinders it indicate a problem on that cyl.<br />Rule of thumb - a 25% lower compression on a cyl compared to highest value you get on a cyl in a test indicate a problem.<br />If the no 1 and 2 cyl got no lubrication because the oil injection failed while running the outboard it could have damaged the cyl, piston, rings, bearings.

On what part do you place the veiner to measure the height? Manual says .91",seams a little much. Due you measure to the bottom or the top of the float? I found out that the whole fuel system needed to be redone. That's why I'm asking.